Best Business mail app out for use on iOS devices

I made the switch from the stock iOS mail app after getting frustrated about having such difficult adding attachments and working with sub-folders. I have been able to solve both issues and much more using mail+ (for both iPad and iPhone).
Bad: every once in a while, the app would encounter a hiccup (e.g. starting up when you have a very weak data signal)
Good: the dev team is constantly working and getting the bugs worked out. They are open to suggestions and do a pretty good job of working in further improvements.

Acilius about Mail+ for Outlook